Continental C90-12F Engine use of autogas

[8466]

I have recently purchased a 1946 140 with C90-12F engine and it has a STC for autogas. I'm a little nervous about using autogas because it might reduce the life the engine. Is this true or does 100LL reduce the life of the engine?

Thayne

[8424]

Well, Thayne, everyone has an opinion, so I'll throw mine out there.

I don't believe either auto fuel or 100LL reduces the life of the engine if the engine is operated correctly. I think dirty oil and dirty air are far more likely to damage it than the fuel. However, I also believe there is a possibility of valve problems with both fuels if not operated correctly.

My son and I put over 400 hours on my C-90 C140 using both auto and 100LL without any problems. Here's the conversation starter: we faithfully used Marvel Mystery Oil as a fuel additive and never had any valve problems. I have always used MMO in my engines, Franklin 150 hp in the Stinson (400 hrs), O-200 in the C150 (200 hrs) and the C-90 in the C140. I also used auto fuel/100LL in the Franklin and O-200. I religiously leaned from start up to shut down to reduce plug fowling with each engine. I will treat the O-200 in my C140A I'm working on the same way.

I have a cousin that flies 2,000 hours per year doing pipeline patrol in a C172. He mixes auto and 100LL 50/50. He majors his engines at 3,300 hrs whether they need it or not! I'm sure some will question those hours, but he's been doing this for 30,000 hours and it is documented.

Now it's someone else's turn to enlighten you!

Steve

[6298]

I have six or eight thousand hours on auto gas in my 140’s. Like Steve said, the plugs will have less lead fouling. The best thing for the long life of our engines is frequent oil changes. Every 25 hours is my recommendation.

[6183]

I was going to add that my good friend Randy Thompson has thousands of hours flying with autogas, and he hasn't reported having any issues; however, he already chimed in on the subject.

I think the big issue is where are you going to operate from? Some municipal airports with fire chief's driving around the area ban aircraft owner's refueling any aircraft with gas cans that most people use when using auto gas. If you've got one of those nice tanks on wheels with an electric pump that you sometimes see, the chief would be gunning for you with one of those also. Now if you operate from a private airport or uncontrolled field out in the country you probably won't get as much hassle. If you're lucky enough to operate from your own airport like Randy, you can pump or pour to your heart's content.

You added a question if engine life is reduced by using either 100LL or autogas. Neither will reduce the life of the engine. Randy has stated that he likes to change oil on a routine basis of every 25 hours, and I tend to agree; however, if you want to go to TBO or more you need to fly the airplane on a routine basis, the more the better. Inactivity is the worst thing that one can do to an engine. One hundred hours per year may sound like a lot, but that's better than 25 hours per year.